1. Field of the Invention
This invention relates generally to the field of computing technology and more particularly concerns the optimizing of memory resources during the initialization routine of a computer system which prepares the system for the loading of an operating system.
2. Description of the Related Art
During a computer system's initialization routine, commonly referred to as a boot sequence, a variety of diagnostics are performed to ascertain the availability and status of hardware devices and ensure proper operation of components. For example, during initialization, a system BIOS executes a boot program which invokes a series of system checks to ascertain the location, number and identity of various devices connected to the computer system. The processing components may be a variety of host adapter cards including, by way of example only, a video display adapter, a network adapter, a SCSI adapter or other similar device. Further, these host adapters cards may either be non-processor based, such as some SCSI and RAID controllers, or may be processor based, such as some high end or low end RAID controllers.
In any event, each of these processing components have an associated option ROM BIOS chip 20, as shown in FIG. 1A. The option ROM BIOS chip 20 includes program instructions known as the option ROM BIOS, and is also referred to herein as a BIOS image 22. As the need for more functionality in the initialization process continues to grow, the BIOS image 22 necessarily grows in size. A typical size of a BIOS images 22 utilized in RAID controller applications is about 64K. The contents of the BIOS image 22 includes, among other things, a header, memory allocator code, decompressor code, runtime code, initialization code, and configuration utility code. A typical processor-based RAID controller, such as the AAA-130SA ULLTRA WIDE SCSI RAID Card manufactured by the Adaptec, Inc. of Milpitas, Calif. may have a compressed BIOS image size of approximately 64K.
At boot-up, the system BIOS loads the BIOS image 22 to the system RAM 40. As is well known, the BIOS image 22 is loaded to an area of the system RAM that is dedicated for this use. As shown in FIG. 1B, a hexadecimal address range between C800:00 and DFFF:00 is often referred to as option ROM memory space. For discussion purposes, it should be assumed that BIOS image-1 22a represents the copied 64K BIOS image 22. Once the BIOS image is copied to this memory space, selected portions of the BIOS image are decompressed and copied to conventional memory 42. The decompressed code is then implemented to initialize the host adapter associated with the option ROM BIOS chip 20.
Although no problems arise during the initialization of option ROM BIOS chip 20, there many situations in which a computer system needs to initialize several option ROM BIOS chips. Because the size of the BIOS image continues to grow, the option ROM memory space can be quickly consumed. This problem is pictorially illustrated in FIG. 1B, where four BIOS images 22a, 22b, 22c and 22d need to be copied to the option ROM memory space. In this example, BIOS image-1 22a, BIOS image-2 22b, and BIOS image-3 22c were successfully copied, however, BIOS image-4 22d did not fit within the fixed option ROM memory space. As such, the controller having the BIOS image 22d will not be initialized. Of course, if a controller is not initialized, the devices (e.g., hard disks, CD-ROMs, etc.) connected to the controller will not be available to the .user of the computer system.
Were system BIOS to encounter uncompressed BIOS images, there might also be a problem because these uncompressed BIOS images might occupy a footprint of more than 64K. This would initially occupy even more memory when initially copied from an associated option ROM BIOS chip into the option ROM memory space. This problem of in insufficient memory is further exacerbated by those systems operating in a BIOS boot specification (BBS) environment. In BBS, the system BIOS actually passes through an option ROM twice during a boot sequence, and each time the option ROM has a different size.
In view of the foregoing, what is needed is a new and improved methodology for conserving memory resources available to a computer system during execution of the system BIOS in order to reduce the amount of memory area that is occupied by the system's various BIOS images. Such an approach would thereby ensure proper initialization of the computer system.
In addition, there is a need for a new methodology for accessing and allocating conventional memory for use by the system BIOS so more memory resources are available to the computer system during initialization and reconfiguration.